Of the radio-elements, radium is one of those with the strictest discharge standards. Many effluents from the extraction of minerals or from the processing of mineral materials are likely to contain radium. That is true of uranium-containing minerals. It is also true of the liquid and semi-solid effluents obtained from the dissolutions and the various washings of zirconium carbochlorination equipment and from the zirconium and hafnium separation processes, for example the separation of zirconium tetrachloride and hafnium tetrachloride by molten salt distillation techniques and by liquid-liquid extraction (MIBK, HCNS), effluents in which a very small amount of radium is generally present.
Radium has the disadvantage of being soluble in water and of being very readily lixiviable, which makes it difficult to store in a dumped solid or semi-solid effluent (sludge).
There are known, for example from U.S. Pat. No. 4,423,007, DE 1005240 or FR2562312, methods for the radium decontamination of or removal of radium from liquid effluents by precipitation of said radium in the form of a double sulfate of radium and barium, Ba(Ra)SO4. These methods are carried out on water or liquid effluents obtained after removal of the substances in suspension, for example by filtration.